Best Of

How do I conduct a Gage R&R study correctly? If I do 3 trials, use 3 appraisers, and 10 parts. Do I want the parts to vary or not? I thought about using gauge blocks rather than parts because I know that they are accurate and what the measurement is. If I have 10 parts do I have my appraisers measure the same 1 dimension on all 10 or measure 10 different dimensions on each part?

I am a first time visitor, helped aboard by Beth and Eric Gasper. I am digging my way backwards through time to the sale of the first gauge set to Cadillac around 1908 and then forward to the AIAG and their method. This is where Don Wheeler says that he first learned it around 1980 or so. I'm wondering what happened in the 70 years between those two points? Also, I recently came across an interesting article by Jody Muelander that says that we should unify Gauge R&R, SPC and the GUM to support future world wide manufacturing measurement demands. Check it out. Glad to be here!

I recently attended an SPC seminar put on by Dr. Wheeler, and one of his
personal experiences involved using SPC to monitor a process that
infrequently had "spills" of varying amounts. From his
book Understanding
SPC, "When events become rare, the counts will be inherently insensitive to
changes in the process". So rather than attempting to chart something
based on a count of your rare events, you may find more success by charting the
amount of time, or number of conforming products that pass between defects.
These can be done with a t-chart, or g-chart respectively.

Thanks, Matt, On what to chart, if I was the employee, I would ask management for their guidance or offer suggestions based on the training I was provided to include identifying the theory as to the "why." If management wants a chart showing zero, then keep providing the chart. I would hope someone in management could answer the question regarding the economics and priorities.

I recently had a conversation
with a customer who was collecting defect data each shift and charting it as
a percent. The “problem” was that for this chart, she had
ten consecutive days with zero defects. The thirty samples (10 days x 3
shifts/day), shows a flat line and no control limits. Since
there is no variability in the data, the standard deviation is 0, therefore control
limits can’t be calculated. She further explained that they are “required” to
chart this data. What would you recommend she do in this case?

I can think of a few options
such as:

1.
Ignore the
‘requirement’ to chart this since charting this does not add value.

2.
Change the time
period how defects are counted. For example instead of each shift, count them
each day.

3.
Show the control
chart with no control limits and all of the data at 0.